With the development of the wireless communication technology, intercom apparatuses have gradually become a common communication tool in today's society due to advantages such as low call costs, not limited by the network, and allowing a plurality of people to have a dialogue at same time. When a plurality of users use intercom apparatuses, they can adjust current operating frequencies of their intercom apparatuses to a same operating frequency for sending and receiving speech signals, realizing communication among many people.
However, when another user having an intercom apparatus also adjust his intercom apparatus to the operating frequency, a speech signal sent from this user can be received by intercom apparatuses of the plurality of users, which is called an unknown speech signal for ease of description. The unknown speech signal may interfere with the plurality of users. At this time, the plurality of users may need to manually adjust current operating frequencies of their intercom apparatuses to another operating frequency, thus avoiding interference of the unknown speech signal.